29 Jan 2009

Sludge on Your Veggies

"A nationwide survey of sewage treatment plants shows that the sludge they produce--the residue from cleaning up wastewater--contains a wide variety of toxic metals, pharmaceuticals, flame retardants, and other compounds, including some antibiotics in surprisingly high concentrations. That's significant because every year more than half of the roughly 7 million metric tons of these so-called biosolids produced in the United States are applied as fertilizer to farm fields."

The EPA wanted to allow sludge to be used at organic farms, but the practice is not allowed.

Bottom Line: Wash those veggies!


  1. So, what should we do with all that sludge? Spraying it on veggies is obviously not a good idea. How much does composting clean it up? Feeding it to worms?

  2. David, have you looked into the processing and treatment that goes into producing the biowaste that is permitted for use on farms? Heavy metal contamination is a concern--pathogens rarely.

  3. Jeremy and Matthew -- I don't have good answers, since I am not a scientist.

    I am guessing that the worst stuff (heavy metals) has to be separated and/or put into toxic storage. There may be some "nice" bacteria that can take care of the problem...

  4. Another timely topic since we have just been approached by a company that wants to spread it on our fields. The material and all associated transportation and application costs are free to the grower. The material has to be incorporated within 3 hours because of a new air board rule. There are a lot of restrictions on when a food crop can be planted on a field that has used sludge, so I don't see how it will be so dangerous (you should probably wash your veggies regardless). The material cannot be spread unless the analysis of the material meets certain criteria and most of the heavy metals are ND (non detectable). The limiting factor is nitrogen, because they can only apply the amount of sludge that whatever the crop is will use (PAN - Plant Available Nitrogen).

    Now that egg and chicken production will be forced out of California by Prop 2 (yes, all you who voted for it did nothing for the chickens except move them out of California), the cost of chicken manure will increase and more will look to alternative sources of organic matter and nitrogen. Keep the sludge coming!

    1. ..and this prediction ("forced out") was wrong:


  5. Good memory David! I had forgotten about this. Always good to look back and I can admit being wrong.

    It did "force out" the traditionally inexpensive supply of eggs for the California consumer - easy for folks with enough disposable income to make regulations that impact low income families. Egg prices more than doubled and are still high - a good source of low cost protein made a great deal more expensive.

    "Operating cage-free facilities increased costs per dozen eggs by 36 percent compared with battery cages, according to a March 2015 study by the Coalition for Sustainable Egg Supply"

    It also turned California egg farmers into activists that went after egg producers in other states so that they would have to change practices as well. HSUS is a radical activist group that cloaks itself as a mainstream animal care group.

    Consumers that care about the well-being of chickens should be able to choose cage free if they like, but the average consumer should still have access to this important protein source at a reasonable price. Shouldn't economics be allowed to work?

    It also cut egg production in California by about a 1/4 - so I guess 75% wrong is still wrong enough.

    1. A 1/4 cut is not too high a price to end a practice that's not sustainable... just like a 25% cut in American consumption, say, would not be too high a price to protect water and air from pollution, or prevent climate change. "Cheap" isn't always the right price ;)


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